Control of tar spot of maize and its effect on yield

Abstract

Abstract The tar spot disease complex of maize and the effects of fungicides on disease development were examined during the November‐April 1988 cropping season in Mexico. The disease is caused by two fungi, Phyllachora maydis Maublanc and Microdochium maydis Muller & Samuels (teleomorph = Monographella maydis Muller & Samuels). The ascostromata of P. maydis can be observed on the lower leaves of the plants generally 10–18 days before silking. M. maydis the second fungus involved in the complex, was found in infected tissues 10–14 days after ascostromata formation. Lesions subsequently enlarged, appeared water‐soaked, and coalesced to cause leaf blight. Application of the fungicides Captan, Fenpropimorph, Carbendazim, Mancozeb, and Propiconazole significantly reduced the area under the tar spot disease progress curves, which in turn significantly increased grain yields. Fenpropimorph resulted in the lowest overall disease severity but not the highest yield. Disease severity in plants sprayed with Mancozeb was not significantly different from that in plants sprayed once with Fenpropimorph, but the former treatment resulted in higher yields and a lower incidence of Fusarium stalk rot.